1. Field of the Invention
The present invention pertains to a method for manufacturing a fiberscopic catheter, which is also called an endoscopic catheter, and which is used in the endoscopic viewing of relatively slender tubes in the body such as blood vessels.
2. Description of the Prior Art
An example of conventional fiberscopic catheters are disclosed in Tokkai (Patent Disclosure) Sho 63 (1988)-119732. The fiberscopic catheter is equipped with an optical glass fiber bundle and the catheter is inserted in the body of a patient just like a regular catheter. Obviously, it is desirable for the catheter to be as slender as possible to minimize pains and injuries to the patient during its insertion. Also, a more slender catheter improves its usefulness in facilitating endoscopic observation of blood vessels or fine tube lumens.
Accordingly, various attempts have been made to reduce the outer diameter of the fiberscopic catheter without downgrading the quality of the images it produces. Such attempts include making finer optical glass fibers and making the fiberscopic catheter more compact by fusing the body of the catheter to the optical glass fiber bundle.
In addition, methods for improving the range of view by blocking the blood flow to provide an unobstructed view from the end of the fiberscopic catheter have been attempted. In this method, a multi-tubed fiberscopic catheter is utilized in which a balloon portion is included at the tip of the fiberscopic catheter. In particular, after the catheter's tip is inserted to the prescribed position in a blood vessel, the balloon portion is expanded to block the blood flow. An example of such a multi-tubed fiberscopic catheter was reported in MEBIO, Medical View, Inc., September 1990, pp. 107-114.
As described above, the conventional method for inserting and tightening an optical glass fiber bundle in the specified lumen of a fiberscopic catheter requires that the diameter of the lumen be greater than the diameter of the optical glass fiber bundle. However, such a method of manufacture generally results in a fiberscopic catheter having a large gap between the outer diameter of the optical glass fiber bundle and the inner wall of the catheter lumen. A fiberscopic catheter having such a large gap between the optical glass fiber bundle and the inner wall of the catheter will mean that the catheter's outer diameter will be unnecessarily large. This contradicts the demand for minimizing the overall diameter of the catheter for ease of insertion into a patient's blood vessel.